In printing, copying, scanning, and other applications, the use of continuous tone (contone) image encoding has been known and used to generate high-resolution or high-color renderings of image files. Contone images can be based on image files whose data specifies color or shade values for each pixel using an arbitrary, or large, range of color values. A continuous or near-continuous range of colors can therefore be presented on color printers, computer monitors, and other output devices.
Besides the corresponding large demands for storage of contone images, additional considerations may affect the suitability or performance of systems designed to print or otherwise output contone-based files. For instance, for an image which is initially captured in RGB (red blue green) color values, then converted to LAB (lightness with a and b color opponent dimensions), a front-end two-dimensional (2D) filter can be applied to sharpen the image initially, before further image manipulation and conversion to binary (i.e., 0 or 1 white of black) values. Images which are processed in that type of image path, but then sent to an output device such as a printer which operates on binary data extended to continuous tone (BDEC) file types, will require a back-end (second) filter in order to arrive at the BDEC output.
In actuality, however, in order to generate a BDEC encoding of an image for printing or other output, the back-end filter must generally apply a low-pass filtering process. The low-pass filter is needed to derive the ultimate contone representation which can be sent to a rendering engine or other final stages in printers or other devices which expect contone-based image files. In known printers or other devices of this type, the back-end filter is fixed to a set value to generate the BDEC-based output. In practice, the effect of the low-pass back-end filter is to blur or smear some details of the image, since some high-frequency edges or other features will not be passed. The user's desired sharpness settings, which may be configured to cause an adjustment in the front-end filter, can therefore be defeated, or partially defeated, by the action of the necessary back-end BDEC filter. The user may therefore not receive exactly the type of sharpness in the printed output, or other output, that they desired.
In addition, in known systems using this general type of BDEC-based image path, the imaging logic can segment or separate different sections of an image into image areas and text areas, in an effort to preserve the legibility of textual portions. However, the imaging logic can at times make mistakes in the classification of textual sections, for instance labeling or identifying some of those sections as an image area, when it is in fact a section of text. When a text segment is classified as an image area, and then sent downstream to the back-end BDEC filter, the low-pass effect of that filter can blur or smudge the pixel-based rendering of that text, to a point where that text is no longer legible. This is particularly true for text segments that are presented in a small font, or which involve special characters or symbols.
it may be desirable to provide methods and systems for dynamic sharpness control in system using binary to continuous tone conversion, in which the user of a printer or other BDEC-based output systems can make a sharpness selection for their desired output, and have that sharpness setting automatically change the filtering characteristics of the back-end filter to better preserve sharpness and detail.